Smoking and other pre-gestational risk factors for spontaneous preterm birth

Abstract

OBJECTIVES: to investigate pre-gestational risk factors for spontaneous preterm birth and, the role of smoking and its cumulative effects on prematurity. METHODS: a case-control study analyzed a data set of all births occurring in a tertiary maternity hospital between April 2002 and July 2004. Spontaneous preterm births of single and live newborns without malformations were selected as cases. Controls were all the term births of live and single newborns without malformations during the same period. Three outcomes were studied: all preterm births (<37 weeks), less than 35 weeks and less than 32 weeks of gestational age. Logistic regression was used to obtain the independent effect of pre-gestational risk factors. RESULTS: maternal age of less than 20 years, low schooling, low maternal pre-gestational body mass index and smoking showed significant, independent association with spontaneous preterm birth for the three outcomes. For all these risk factors, excepting maternal smoking, odds ratios increased with decreasing gestational age at birth and this trend was significant for low maternal age and low pre-gestational body mass index. CONCLUSIONS: the cumulative effects of smoking calls for the need to encourage smoking cessation among pregnant women, especially those who are underweight and in the older age groups, because of the increased risk of delivering premature babies.

Maternal Risk Factors for Preterm Birth in Murmansk County, Russia: A Registry‐Based Study

“…Our findings demonstrate that maternal factors which enhance the PTB risk were similar for all three groups, and this is consistent with other studies . More specifically, we observed a strong association between unmarried status and increased risk of PTB at any GA as others have .…”

“…Our observation that the prevalence of being single or cohabiting was the lowest for term births coincides with a Finnish study. Similarly, our findings regarding the effect of maternal smoking agree with earlier studies . Smoking as a risk is not surprising since, in addition to nicotine and carbon monoxide, cigarette smoke contains many potentially organic toxic substances (e.g.…”

“…Similarly, our findings regarding the effect of maternal smoking agree with earlier studies. 14,21,22 Smoking as a risk is not surprising since, in addition to nicotine and carbon monoxide, cigarette smoke contains many potentially organic toxic substances (e.g. tars and other organic compounds) in addition to toxic metals, hydrogen cyanide, and nitrogen oxides.…”

“…General infection, drug abuse, and mental disorders are all indicated to be major contributors to extremely and very preterm spontaneous PTB with intact membranes, as does maternal tobacco smoking during weeks 27–33 . Pre‐existing or gestational diabetes, general infection, drug dependence, and mental disorders are known systemic co‐morbidities associated with spontaneous PTB at 32–36 weeks, while risks due to maternal young age, incomplete secondary education, and low BMI are enhanced at lower GA …”

“…17,18 Stillbirth, major congenital anomalies, placenta previa and abruption place women at a higher risk of PTB independent of GA. 19 General infection, drug abuse, and mental disorders are all indicated to be major contributors to extremely and very preterm spontaneous PTB with intact membranes, 20 as does maternal tobacco smoking during weeks 27-33. 21 Preexisting or gestational diabetes, general infection, drug dependence, and mental disorders are known systemic co-morbidities associated with spontaneous PTB at 32-36 weeks, 20 while risks due to maternal young age, incomplete secondary education, and low BMI are enhanced at lower GA. 14 Internationally published data on prevalence and risk factors of PTB in Russia are limited. Low level of maternal education, maternal stress, placental disorders (abruption/antepartum haemorrhage and placenta previa), and history of antenatal fetal loss have been identified to increase spontaneous PTB risk in Severodvinsk.…”